1. Field of the Invention
This invention relates generally to a blood collection apparatus and a method for using the same. In particular, this invention relates to a blood collection apparatus for making an incision in the scalp of a fetus and collecting blood resulting from the incision in a capillary tube attached to the device in a manner in which the blood being drawn into the capillary tube can be viewed.
2. State of the Art
Collecting blood from an infant during the birthing process is employed extensively when the doctor suspects an infant is not receiving an adequate supply of oxygen due to strangulation of an umbilical chord or premature separation of the placenta. Fetal blood sampling conventionally involves passing an amnioscope through the birth canal and pressing it onto the fetal presentation, creating a xe2x80x9ccofferdam sealxe2x80x9d between the fetal scalp and a distal end of the amnioscope. A lance, long-handled scalpel, or other similar scalp-puncturing or incising instrument is then introduced through the amnioscope to make an incision. The blade is kept perpendicular to the surface of the scalp, and the puncture or incision achieved by a sudden thrust forward. After the scalp puncture is made, the scalp-puncturing instrument is removed and a long capillary tube, or a short capillary tube at the distal end of a holder, is advanced inside the amnioscope to collect a sample of the blood from that exuding from the scalp. Finally, the sample of blood is transferred from the long capillary tube into a special capillary tube designed for use with blood gas analysis equipment. If a short capillary tube is used, it may be configured for compatibility with blood gas analysis equipment and used directly therewith.
This procedure, however, is relatively time consuming under the circumstances of child birth, and exhibits a high potential for error due to the exchange of multiple instruments. Further, other areas of concern are lack of careful control of the depth of the incision (preferably no deeper than 2.5 mm) and the avoidance of contamination from the transfer of blood from the sampling tube to the analysis tube.
A blood collecting device disclosed in U.S. Pat. No. 4,360,016 to Sarrine addresses some of the problems discussed above by disclosing a single device that performs both the functions of puncturing a fetal scalp and collecting blood resulting from the puncture. In particular, Sarrine discloses a tubular member with a collar at its distal end and a head at its proximal end, the head being spring-biased away from the proximal end and having a catch or tab to hold it against the bias. In addition, at the distal end of the tubular member there is a wedge slidably mounted therein and connected to the head by an intermediate rod, the wedge carrying a lancet blade projecting distally from its distal end. A capillary tube for collecting blood is clipped in a recess in the side of the tubular member with the distal end of the tube located directly underneath the lancet blade and encircled within the collar. In use, the distal end of the tubular member is placed against the fetal scalp, after which the spring-loaded head is depressed, moving the wedge distally a predetermined distance to puncture the fetal scalp. Blood resulting from the puncture is then asserted to pool within the lower portion of the collar, where the blood is drawn by capillary action into the bore of the capillary tube.
However, there are several problems associated with the device disclosed in Sarrine. For example, since the capillary tube is located within a recess in the side of the tubular member and is rotationally disposed at the underside of the tubular member as the device is used, the tubular member obscures any view of the capillary tube so that it is impossible to determine if and when blood is being collected, or when the capillary tube is sufficiently filled without withdrawing the device from the mother. This drawback will often necessitate in reiterating the procedure of puncturing the scalp of the infant until an appropriate blood sample is collected. Further, there is the potential problem of damaging the capillary tube or contaminating the blood sample when extracting the capillary tube from the recess in the tubular member after the blood has been collected because the distal end of the capillary tube is encircled by the collar and the clips holding the tube are located within the recess. In addition, Sarrine does not necessarily place the capillary tube on the device in a position designed to collect blood at the highest efficiency.
In overcoming the deficiencies of the prior art, the present invention provides an apparatus for making an incision in a fetal scalp and efficiently collecting blood emanating from the scalp incision in a capillary tube while facilitating visualization of the tube during the collection process.
In addition, the present invention provides an apparatus for incising the fetal scalp of a design from which the capillary tube can be easily removed from the device to limit potential damage of the capillary tube or contamination of the tube or the blood therein.
The present invention also provides an apparatus on which the capillary tube can be easily and precisely positioned with the tube located and oriented to collect blood efficiently.
The present invention comprises an elongated, substantially tubular housing with a proximal end, a distal end and a bore extending longitudinally therethrough. A plunger which includes a proximal portion extending beyond the proximal end of the housing, which is proximally spring-biased and has associated therewith a catch and a release element, is slidably disposed in the proximal end of the elongated housing, which may comprise a biasing mechanism formed separately from the remainder of the elongated housing. An extension member 54 is secured to the plunger and extends distally within the bore of the elongated housing. A blade assembly is secured within the bore to a distal end of the extension member 54 and is extendable beyond the distal end of the elongated housing responsive to longitudinal pressure applied to the proximal portion of the plunger. A groove is formed in an exterior surface of the elongated housing proximate the distal end to receive a side of a capillary tube placed on the housing and retained thereon with a retention element. The groove may be parallel to the longitudinal axis of the housing, or may be oriented at a small, acute angle thereto so as to provide a three-dimensional perspective and facilitate viewing of blood traveling up the capillary tube.
The groove on the elongated housing exterior includes a recessed, shallowly cupped or spooned region proximate the distal end thereof. Further, the groove is preferably formed to a predetermined length so that when the capillary tube is received within the groove, the distal end of the capillary tube is disposed at a proximal end of the recessed region. Furthermore, the groove has associated therewith a channel across and transverse to the groove disposed adjacent to the distal end of the groove but proximally of the recessed region. The channel extends more deeply into the elongated housing than the groove so as to prevent wicking of the blood toward a proximal end of the groove under a capillary tube disposed in the groove.
The blade assembly includes a beveled blade which is configured to initiate an incision in a fetal scalp with minimal force by effecting an initial penetration with the sharp tip of the blade and enlarging the incision as the blade penetration increases and a greater width of blade enters the scalp. In addition, the blade member includes a blade stopper to limit the depth to which the blade may puncture the fetal scalp.
The apparatus of the present invention may also include a light source attached thereto at the distal end of the housing, or a light source which is projected to the distal end of the housing from the proximal end thereof, optionally using a transparent or translucent housing material as a projection element or wave guide to facilitate viewing of the fetal scalp as well as back-lighting the capillary tube from the exterior of the housing.
The present invention also includes a method for collecting blood in a capillary tube from a fetal scalp, comprising advancing a fetal blood collecting apparatus into a cervix so that a distal portion thereof is located proximate the scalp of a fetus with the capillary tube on an exterior portion of the apparatus, incising the fetal scalp and causing the blood to pool at the distal end of the apparatus, viewing blood from the pool being drawn into the capillary tube and withdrawing the apparatus from the cervix after determining that a sufficient amount of blood has been drawn into the capillary tube. The method preferably but optionally includes retracting a blade employed to incise the fetal scalp after the incision is effected.